Without limiting the scope of the invention, its background is described in connection with the delivery to specific target tissues.
Intravenous injection of therapeutics for the treatment of cancer is considered the ultimate therapeutic because all tumors and their metastases are sustained by blood vessels. These tumor vascular beds are leaky enough to allow liposomes direct access to tumor cells. Anti-angiogenic drugs or gene therapeutics delivered to the tumor vasculature could be used to block the blood supply to tumors, thereby causing tumor regression.
Targeted delivery is essential for greatest efficacy and reduced toxicity. The major constraints on the broad therapeutic applications of most liposomal delivery systems are their poor transfection efficiencies in vivo, accumulation in the lungs after intravenous delivery, aggregation, clearance after systemic delivery (e.g., by Kupffer cells), inability to deliver the bulk of injected liposomal complexes to the target cells and organs, and other issues. Targeted delivery for treatment of cancer is further complicated by the lack of known cell surface receptors to use for efficient targeting.